The invention relates to a method for improved sequencing of letters in mail-sorting facilities.
In mail-sorting facilities, mailed items, particularly letters, are sorted in a pre-sorting procedure and deposited into a number of stacking compartments. The extent of sorting that can be achieved is determined by the number of stacking compartments into which the mailed items are distributed. Often it is neither desired nor possible, for practical reasons, to provide each of the smallest classes of a sorting procedure with its own sorting compartment. For example, when the mailed items are to be sorted corresponding to the sequence of a distribution in the postal route, a separate sorting compartment for each mail recipient is not necessary. Rather, the mailed items are distributed into a specific number of stacking compartments in the same sequence in which they will later be distributed by the sorter during the distribution process. The mailed items are arranged inside each sorting compartment to correspond to the stipulated sequence so that, in a corresponding arrangement of the stacking compartments, all of the mailed items are arranged according to the stipulated sequence. To permit sorting facilities to use a relatively small number of stacking compartments, the mailed items are sorted multiple times and possibly indirectly, as described, for example, in the Proceedings USPS Advanced Technology Conference, Washington, D.C., of Dec. 2, 1992, pp. 1061-1974.
Mail-sorting facilities are known in which the stacking compartments are disposed opposite the mail input, so that after each sorting procedure that is followed by a further sorting procedure, the mailed items can be quickly taken manually from the stacking compartments and reinserted into an input module. In manual transfer, the mailed items are respectively transferred by the handful from the compartment into containers opposite the stacking compartments and that are mounted on a mobile base. It is conventional that the containers possess a larger holding capacity than the stacking compartments, which must be emptied multiple times for transfer during each sorting procedure. A prerequisite for sequencing in accordance with the above-described method is that the sequence of the parcels be strictly maintained, i.e., the sequence integrity after the first and all subsequent sorting procedures. It is thus necessary that the containers be brought back into the correct sequence after each sorting procedure with the mobile base or additional transport means for mail input, or sorted into suitable groups for further processing after the last sorting procedure. Particular drawbacks of the prior art are that at least two operators are required for mail input and emptying the compartments. Further, restacking or interim stacking of the mailed items in containers requires a greater space requirement and increases the risk of disturbing the sequence integrity, because the stacks in the containers can easily capsize when the container is only partly filled, and the produced sequence can thus be disturbed. Further, the stacks can inadvertently be loaded into the wrong containers, or the sequence of the containers can be disturbed.